If you need to remove an announcement from your course, you can easily delete it in Canvas.
Delete in Announcements Page
To delete an announcement from the index page, locate the announcement. Click the Options icon  and click the Delete link .
To delete multiple announcements at a time, click the checkbox next to the announcements you want to delete  and click the Delete button .
Delete in Individual Announcement
To delete an announcement individually, click the title of the announcement.